A system for the pneumatic propulsion of cargo or passenger vehicles is disclosed in Brazilian Pat. No. 7,703,372, filed on May 25, 1977 (25.05.77). This system consists of a tube equipped with a longitudinal slot with a sealing system through which passes a rod or shaft attached to a set of fins on the chassis of the vehicle, supported by the tube, with the propulsion being provided by means of an airflow of high-speed acting on the set of fins, propelling it and, as a result, moving the vehicle freely, by means of devices that are adequate to enable this movement/motion, with the flow in question being generated by stationary sources located outside the vehicle, with the system in question also including brakes that act directly on the said devices and special conduits for enclosing the electrical and telephone network cables.
The pneumatic propulsion system described above for the transport of cargo or passengers is characterized by the fact that the vehicles are propelled pneumatically by means of stationary units, inasmuch as the system has the following goals: to provide an urban transportation system on a scale that meets current and future needs; to combine, in a single design, optimal characteristics in terms of vehicles, permanent trackway, and terminals; to provide significant progress in economic effectiveness in urban transportation; and to provide speed, regular service, comfort, and safety at reduced costs.
Brazilian Pat. No. 7,906,255, filed on Sep. 28, 1979 (28.09.79), proposed an improvement in a pneumatic propulsion system for cargo vehicles and passenger vehicles. This improvement consisted of a propulsion duct which, in addition to serving as a channel for air for the propulsion of the vehicle, also had the additional function of providing the necessary structure for installation in the elevated network of the transportation system, i.e., its own structure for the propulsion duct, consisting of a single channel in conjunction with tracks or rails forming an integral part of the said structure, thereby making unnecessary any other structures for the support of the rails, except the structures for supporting or keeping the main structures above the ground, spaced at sufficiently large intervals so as not to interfere with surface traffic.
Another important characteristic of the system is that when a suction regime is established in the duct, the difference between the internal and external pressure acts to compress a flexible flap against a stop, sealing the longitudinal slot in the duct, and at the same time allowing the passage of the articulation arm of the fin of the vehicle through a mechanical gap, such that because of its flexibility, this flap provides an adequate seal even under over-pressure conditions in the duct, with a system also being provided for the relief of the internal pressure within the propulsion duct.
The system in question is also equipped with a flow alternator mounted in conjunction with each blower, in combination with a flow control valve, by means of which the airflow conditions within the duct can be controlled, which in turn determine the back and forth movements of the vehicle by remote control, as a function solely of the commands issued to the flow alternator. The system in question also includes a set of valves at each station, positioned such that they provide control means for a safety system that ensures the positive separation of two vehicles under any circumstances.
Brazilian Pat. No. 83 01 706, filed on Apr. 4, 1983 (04.04.83), describes improvements in a pneumatic propulsion system for cargo vehicles and/or passenger vehicles. In the pneumatic propulsion system in this invention, the vehicle is controlled through the regulation of the airflow in the propulsion air duct, with this type of regulation being implemented by means of butterfly-type control valves, in association with a single airflow generator. Through their position, these valves determine the direction of the airflow in the duct, its speed, and the pressure differential (within the discharge and pressure range of the generator unit). A set of four valves associated with the generator unit connects the suction and exhaust manifolds to the air propulsion duct and to the atmosphere.
The documents cited above do not provide sufficient means for adequate control of the movements of vehicles along the line. The operation of a pneumatically controlled propulsion transportation system requires that control elements be provided for maintaining adequate vehicle frequency, regulating vehicle traffic, ensuring the effective movement of vehicles over the entire length of the line, and establishing safe conditions for the vehicles during operation, along with other equally important factors.